Conventionally, in order to test electrical characteristics of IC chips formed on a semiconductor wafer, a probe test is performed on the wafer by using a probe apparatus. The probe apparatus includes a wafer stage capable of moving in X, Y and Z directions and rotating about a Z axis and is configured to test the electrical characteristics of the IC chips by brining probes, e.g., probe needles, of a probe card provided above the wafer stage into contact with electrode pads of the IC chips of the wafer, and controls a position of the wafer stage so that the probe needles are brought into contact with the electrode pads. The wafer stage is driven in X, Y and Z directions by a driving unit, and the position thereof is controlled by linear scales provided on three stages moving along X, Y and Z directions which mount thereon the wafer stage or by a detected value of an encoder of a pulse motor (value calculated based on a detected pulse). In other words, the wafer stage moves on coordinates of a driving system managed by the detected value.
After a camera picks up images of specific points on the wafer and the probe needles, the position (contact position) on X, Y and Z coordinates of the driving system to bring the electrode pads of the wafer into contact with the probe needles can be obtained by a computation based on the position of the camera and the result of the picked up images. Next, the probe needles are brought into contact with the wafer. In that state, the wafer stage is slightly raised so as to apply an overdrive to scratch a natural oxide film by the probe needles. The test is performed while contacting the probe needles with the electrode pads (Patent Document 1).
In this probe apparatus, when the test is carried out, the wafer stage for mounting thereon the wafer may be heated to a predetermined temperature (set temperature) and, thus, the wafer stage may be provided with a heating unit and a temperature detecting unit.
Further, when the test is performed by heating the wafer, the contact position is determined by a computation after confirming that the temperature detecting unit has detected that the surface of the wafer stage has been heated to the set temperature to control the position of the wafer stage. However, when the wafer stage has been heated, even if the surface of the wafer stage has reached to the set temperature, a long period of time is required to uniformly heat an entire stage assembly (XYZ table) including the wafer stage. As a consequence, the coordinates positions of the mounting surface of the wafer stage keep changing after the images picked up by the camera, e.g., during the measurement.
Due to the miniaturization of the electrode pads, if the actual contact position between the electrode pads and the probe needles is shifted from its target contact position in X and Y directions, the probe needles can be positioned outside the electrode pads and, thus, they may not contact with each other securely. Moreover, if the actual contact position between the electrode pads and the probe needles is shifted from its target contact position in Z direction, for example, if the actual contact position is shifted from its target contact position toward the prove needles side, the probe needles can penetrate into the electrode pads. On the contrary, if the actual contact position is shifted from its target contact position toward the electrode pad side, the probe needles and the electrode pads cannot be brought into contact with each other. As a result, the reliability of the measurement deteriorates.
In Patent Document 1, the stability to the temperature change is increased by equalizing thermal expansion coefficients of the base table, the camera and the probe card and arranging the respective components so that the effects of the thermal expansion thereto can be minimized. However, the above problems cannot be solved by the apparatus of Patent Document 1.    (Patent Document 1) Japanese Patent Laid-open Application No. 2004-152916 (Paragraphs 0018 and 0019)